The present invention relates to a system for selecting and reproducing text on a screen of a television receiver which is equipped to record, store and reproduce text infomation and is provided with an operating deivce for program selection and control of the television receiver functions.
This system includes an accessory device which is connected with the television receiver by means of a line and includes a modulator and a demodulator and is provided with an interferace for a telephone and an interface for connecting it to outside the telephone line.
Two such systems have been proposed thus far. They are the Viewdata system originating in Great Britain, from the British Post Office, and the TV-Phone originating in the U.S.A. from Phonics Corporation.
Viewdata is a telecommunication system design in the developmental stage which is intended to enable the user to obtain information from a text data bank. To do this, he establishes a connection with the text data bank. Upon call-up, the text data bank transmits the requested data at a bit rate of 1200 or 2400 bits per second, as is customary in a dial telephone system. After having dialed the address of the specific desired data, there is a certain access time delay before the data appear on the screen. In dialog communications, the desired data is identified, after the dial connection has been established, in a dialog between user and text data bank and is then transmitted to the user.
In the Viewdata system it is proposed to provide for the dialog: firstly, a simple yes/no signaling device; secondly, a simple keyboard, for example, like that of telephones equipped for push-button dialing; and thirdly, a complete alphanumeric keyboard. In the call-up mode as well as in the dialog mode, a connection is established either with an available telephone receiver or with a separate dialing device. It has also been proposed to combine all possible modes of communication into a complex instrument designated the viewdata-phone.
The second prior art video data system, the TV-Phone, has been designed especially for communication between the deaf. The users are able to write in, via a complete type-writer keyboard, a text which then appears on their own screen and on the screen of the receiving user, the text being recorded continuously.
The above-mentioned video data systems require more or less expensive additional keyboard devices which must be connected to an accessory device, the adapter.